The role of salts selection on phase formation and electrical properties of K0.5Bi0.5TiO3 ceramics fabricated via molten salt synthesis

Abstract

The present study reveals the effect of salts (NaCl and KCl) on the chemical composition, structural, and electrical properties of intended K0.5Bi0.5TiO3 (KBT) ceramics fabricated via the molten salt synthesis (MSS) route. The average grain size (∼6 μm (±1.1 μm)) and elemental distribution observed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) on KBT ceramics prepared using NaCl as the salt (named KBT-Na) signify the formation of Na0.5Bi0.5TiO3 (NBT) phase instead of KBT ceramic. The Rietveld refinement on X-ray diffraction (XRD) data and temperature-dependent dielectric behaviour of KBT-Na sample further validate the formation of NBT phase. The obtained results suggest the reaction of NaCl salt during the MSS of the KBT-Na sample. Moreover, the structural analyses of KBT ceramic synthesized using KCl salt (named KBT-K) suggested the presence of a minor Aurivillius phase (K0.5Bi4.5Ti4O15) which could be related to undesired reaction kinetics in MSS. The higher room temperature conductivity (∼10−6 Scm−1) and lower piezoelectric coefficient ((d33) ∼ 4–5 pC/N) indicate the loss of stoichiometry in both KBT-Na and KBT-K ceramics during the removal of salts. The observed results in KBT-Na & KBT-K were systematically compared with pure NBT & KBT ceramics prepared using the conventional solid-state synthesis route. The possible reasons for the lossy behavior of MSS synthesized samples are also discussed.